Substantial areas of land and of submerged land in the world have become contaminated from industrial, waste disposal, farming, logging, military, mining and other activities. The U.S. Environmental Protection Agency (“EPA”) has estimated that 10 percent of the nation's lakes, rivers, and bays are sufficiently contaminated with toxic pollutants to pose potential risks to fish and to humans and wildlife who eat fish. “EPA's Contaminated Sediment Management Strategy,” EPA-823-R-98-001, 1998. According to the EPA, 15 percent of the nation's lake acreage and 5 percent of the nation's river miles are under state-issued fish consumption advisories, including parts of each of the great lakes and a large portion of the nation's coastal waters. See, for example, “Listing of Fish and Wildlife Consumption Advisories”, EPA 823-C-97-004, 1997, “The Incidence and Severity of Sediment Contamination in Surface Water of the United States”, EPA 823-R-97-006, 007, 008, 1998, and “Fact Sheet of April 1998,” EPA-823-F-98-004. Thus, billions of dollars of economic activity are affected by contaminated sediment, including the loss of recreational and commercial fishing grounds and a higher cost of disposing contaminated material that has been dredged to aid navigation.
The wide-spread contamination problem encompasses a diverse range of pollutants, including, for example, chemical compounds (e.g., dioxins, PCBs, pesticides and phenols, many of which are volatile), heavy metals (e.g., lead and mercury), and microbes (e.g., hepatitis, E. Coli, cholera). When on land, the contaminants threaten ground water, thus limiting drinking water supplies and even preventing land re-use. The contaminants also enter and threaten the marine environment, and often are found in sediments of coastal waters.
The United States, the European Community, and other countries have responded to this problem with legislation that pins liability on waste producers, other companies, and even innocent buyers of land that must clean up contamination after its discovery. In many cases the materials are wet and generally are termed “sludges.” For purposes of this disclosure, the term “sludge” means contaminated wet materials such as sediment and also contaminated land, and other contaminated material byproducts from mining, farming (for example, feed lot waste and biomass production and waste) and other activities that generate toxic wet or wet-able mass requiring remediation.
A business, individual or government body having liability for a contaminated sludge is faced with an expensive and often technically complicated task. First, the presence of contaminants in sediment, for example, may prevent normal dredging and disposal of the sediment. Second, physical remediation of the sediment sludge must be carried out in a manner that does not pollute the environment. Third, the material must be disposed of in an environmentally safe manner and, preferably, one that has a societally beneficial use. In fact, whether the activity takes place on land or below the water surface, U.S. regulators charged with environmental policymaking increasing require the party charged with the clean-up to identify a productive, beneficial end use of the contaminated material prior to moving it. In other words, the overall problem flows from the three separate issues of (1) moving, (2) remediating, and (3) disposing of sludge without polluting the environment at each step. The problem is magnified by the immense volumes of contaminated sludges. Cost-effective technology is needed to manage these sludges—and particularly to manage the three areas simultaneously.
Technological solutions have been proposed that address one or more parts of this problem, but are too expensive or yield incomplete results. Numerous procedures are known for moving contaminated sludge, but transported material has to be processed and, in some cases, shielded from exposure to the environment to prevent further contamination of the environment, particularly when volatile contaminants are present. Thus, decontamination technology should take into account transportation, end-use, and cost savings for each of these areas.
Decontamination technology exists for handling sludges, including, for example, ex situ biological treatment (i.e., composting and landfarming), ex situ physical/chemical treatment (i.e., soil solidification, soil stabilization and solvent extraction) and other treatments, such as volatilization, soil washing, pump and treat systems, slurry phase bioremediation etc. Because of the special difficulty in removing organic materials, ex situ thermal treatment (i.e., high temperature thermal desorption, hot gas decontamination, incineration, low temperature thermal desorption, rotary kiln) or biological conversion as described in U.S. Pat. Nos. 4,750,436, 4,079,003, 5,172,709, 5,855,666 may be used to eliminate such contaminants. In each case, however, the procedure and materials for removing a given contaminant is not integrated sufficiently with the removal of other contaminants and with a low cost method that leaves the sludge in a ready to transport form.
The non-comprehensive approaches to remediation exemplified above are not sufficiently low cost or incorporated into a system that isolates contaminants from the environment during processing with conversion into a less-toxic form for transportation to a site for beneficial end use. Transfer of material to a toxic landfill, for example, or its entrapment within a matrix possessing a long (but limited) life is not a permanent solution. Such measures actually may incur future liability as the legal system evolves to address the long-term problem. Further, many, if not most of these processing techniques do not treat a wide range of contaminants. For example, most present biological processes such as composting and air-sparging do not alleviate the problem of toxic metals in the contaminated sludge. Furthermore, some techniques such as soil stabilization, incineration, and pump/treatment generate a large volume of secondary waste that is difficult to control. These procedures are high cost and fairly inflexible with respect to proximity to a particular site.
In sum, the problem of sludge remediation is multifactorial and raises processing concerns such as environmental contamination during remediation processing and movement, low cost transport of material and disposal of remediated material after conversion into an enhanced use form. A more comprehensive method that address all such factors in a low cost manner is needed.